1. Field of the Invention
This invention relates generally to artificial body members and, more specifically, to surgically implantable breast prostheses.
2. Description of the Prior Art
Gel-filled silicone rubber breast prostheses have been employed for a number of years to maintain the natural appearance of the breast and for cosmetic purposes. A typical breast prosthesis of the gel-filled type is shown in U.S. Pat. No. 3,293,663 to Cronin.
While such a prosthesis when properly implanted effects augmentation of the breast, in time the capsule of fibrous tissue surrounding the prosthesis may cause a spherical contracture of the prosthesis into a relatively rigid and tense structure. As the tissues around the implant contract, the fixed volume of the silicone gel material within the container is forced into a shape having the smallest possible surface area, a sphere surrounded by essentially inelastic fibrous scar tissue. The hard spherical prosthesis results in an aesthetically undesirable breast.
Various solutions to this problem have been attempted. Hartley, Jr. (U.S. Pat. No. 3,934,274) discloses a double-walled prosthesis arranged so that some filler material can be released from the compartment between the double walls to reduce its size and to relieve the pressure of capsular contracture. The decompression procedure is accomplished by inserting a hypodermic needle through the breast and into the compartment. The filler material in the compartment is withdrawn through the needle. Such a procedure can be a great inconvenience to the patient. The Hartley, Jr. prosthesis has the additional disadvantage that it does not prevent reoccurance of capsular contraction.
Perras et al. (U.S. Pat. No. 3,665,520) discloses a prosthesis which has an extended shape and which includes a fabric material to increase the rigidity of the back wall of a prosthesis so that the combined shape and stiffness counteract the forces of tissue ingrowth. The prosthesis disclosed by Perras leaves room for improvement. The extension becomes firm and palpable with fibrous tissue ingrowth in some patients and therefore a non-extended shape would be more desirable. Further, it is desirable in many instances to use an implant in which the restraining means functions only in response to tissue pressure.